linux-kernel - Re: [PATCH v3 11/24] iommu/io-pgtable-arm-v7s: Quad lvl1 pgtable for MediaTek

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Date:   Fri, 23 Oct 2020 15:10:22 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Will Deacon <will@...nel.org>
Cc:     Evan Green <evgreen@...omium.org>, Tomasz Figa <tfiga@...gle.com>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, youlin.pei@...iatek.com,
        Nicolas Boichat <drinkcat@...omium.org>, anan.sun@...iatek.com,
        chao.hao@...iatek.com, ming-fan.chen@...iatek.com,
        Greg Kroah-Hartman <gregkh@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v3 11/24] iommu/io-pgtable-arm-v7s: Quad lvl1 pgtable for
 MediaTek

On 2020-09-30 08:06, Yong Wu wrote:
> The standard input iova bits is 32. MediaTek quad the lvl1 pagetable
> (4 * lvl1). No change for lvl2 pagetable. Then the iova bits can reach
> 34bit.
> 
> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>   drivers/iommu/io-pgtable-arm-v7s.c | 13 ++++++++++---
>   drivers/iommu/mtk_iommu.c          |  2 +-
>   2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index 8362fdf76657..306bae2755ed 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -50,10 +50,17 @@
>    */
>   #define ARM_V7S_ADDR_BITS		32
>   #define _ARM_V7S_LVL_BITS(lvl)		(16 - (lvl) * 4)
> +/* MediaTek: totally 34bits, 14bits at lvl1 and 8bits at lvl2. */
> +#define _ARM_V7S_LVL_BITS_MTK(lvl)	(20 - (lvl) * 6)

This should defined in terms of both lvl and cfg->ias. The formula here 
is nothing more than a disgusting trick I made up since a linear 
interpolation happened to fit the required numbers. That said, all of 
these bits pretending that short-descriptor is a well-defined recursive 
format only served to allow the rest of the code to look more like the 
LPAE code - IIRC they've already diverged a fair bit since then, so 
frankly a lot of this could stand to be unpicked and made considerably 
clearer by simply accepting that level 1 and level 2 are different from 
each other.

Robin.

>   #define ARM_V7S_LVL_SHIFT(lvl)		(ARM_V7S_ADDR_BITS - (4 + 8 * (lvl)))
>   #define ARM_V7S_TABLE_SHIFT		10
>   
> -#define ARM_V7S_PTES_PER_LVL(lvl, cfg)	(1 << _ARM_V7S_LVL_BITS(lvl))
> +#define ARM_V7S_PTES_PER_LVL(lvl, cfg)	({				\
> +	int _lvl = lvl;							\
> +	!arm_v7s_is_mtk_enabled(cfg) ?					\
> +	 (1 << _ARM_V7S_LVL_BITS(_lvl)) : (1 << _ARM_V7S_LVL_BITS_MTK(_lvl));\
> +})
> +
>   #define ARM_V7S_TABLE_SIZE(lvl, cfg)					\
>   	(ARM_V7S_PTES_PER_LVL(lvl, cfg) * sizeof(arm_v7s_iopte))
>   
> @@ -63,7 +70,7 @@
>   #define _ARM_V7S_IDX_MASK(lvl, cfg)	(ARM_V7S_PTES_PER_LVL(lvl, cfg) - 1)
>   #define ARM_V7S_LVL_IDX(addr, lvl, cfg)	({			\
>   	int _l = lvl;							\
> -	((u32)(addr) >> ARM_V7S_LVL_SHIFT(_l)) & _ARM_V7S_IDX_MASK(_l, cfg); \
> +	((addr) >> ARM_V7S_LVL_SHIFT(_l)) & _ARM_V7S_IDX_MASK(_l, cfg); \
>   })
>   
>   /*
> @@ -755,7 +762,7 @@ static struct io_pgtable *arm_v7s_alloc_pgtable(struct io_pgtable_cfg *cfg,
>   {
>   	struct arm_v7s_io_pgtable *data;
>   
> -	if (cfg->ias > ARM_V7S_ADDR_BITS)
> +	if (cfg->ias > (arm_v7s_is_mtk_enabled(cfg) ? 34 : ARM_V7S_ADDR_BITS))
>   		return NULL;
>   
>   	if (cfg->oas > (arm_v7s_is_mtk_enabled(cfg) ? 35 : ARM_V7S_ADDR_BITS))
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index f6a2e3eb59d2..6e85c9976a33 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -316,7 +316,7 @@ static int mtk_iommu_domain_finalise(struct mtk_iommu_domain *dom)
>   			IO_PGTABLE_QUIRK_TLBI_ON_MAP |
>   			IO_PGTABLE_QUIRK_ARM_MTK_EXT,
>   		.pgsize_bitmap = mtk_iommu_ops.pgsize_bitmap,
> -		.ias = 32,
> +		.ias = 34,
>   		.oas = 35,
>   		.tlb = &mtk_iommu_flush_ops,
>   		.iommu_dev = data->dev,
>